Patent Literature 1 discloses a motor device including a case, a motor, and a circuit board. The case includes a cover and a metallic base. The motor is located on a surface of the base on the opposite side of a cover mounting surface. The circuit board is located in an accommodation space of the case and is affixed to the cover mounting surface. The circuit board has a circuit to drive a motor. This kind of the motor device is applied to, for example, a valve timing control apparatus, which uses rotation of a motor to control a valve timing of an internal combustion engine.
In the configuration of Patent Literature 1, a heat generating component, such as a switching element of a control circuit, is mounted on a ceramic substrate to construct a circuit board. The ceramic substrate is affixed to a cover mounting surface of a base. The ceramic substrate is arranged to enable to release heat, which is generated by the heat generating component, to the base via the ceramic substrate. In addition, a tall component, such as a capacitor and/or a coil, is mounted on an electric supply plate other than the ceramic substrate.
(Patent Literature 1)
Publication of Japanese unexamined patent application No. 4468033
It is conceivable to employ, instead of a ceramic substrate, a printed circuit board, which contains resin as a base material, in order to reduce a manufacturing cost, downsizing, and/or the like. In this case, components may be mounted on both sides of the printed circuit board. In the present configuration, heat, which is caused by a heat generating component, can be released via a thermal conduction member to a case, more specifically, for example, a base. The thermal conduction member is, for example, heat dissipation gel having flexibility.
In a configuration where components are mounted on both sides of a printed circuit board, an affixation configuration, in which one side of the printed circuit board is substantially entirely affixed to the case, cannot be employed. In a motor device, a motor and a circuit board are integrated together. Therefore, vibration of the motor is transmitted to the printed circuit board. A double-sided mounting configuration, in which components are mounted on both sides of a printed circuit board, may raise a concern about vibration of the circuit board. As a result, the double-sided mounting configuration may raise a concern about reliability of connection of components.
It is further conceivable to equip a vibration suppression member, such as a rubber member, between a printed circuit board and a case in order to restrict vibration of the printed circuit board. However, additional vibration suppression member may increase a number of components and may increase a manufacturing process.